Regulator arrangement for lowvoltage generators



Oct. 5, 1965 H. DOMANN 3,210,645

REGULATOR ARRANGEMENT FOR LOW-VOLTAGE GENERATORS Filed Nov. 14. 1961 3 Sheets-Sheet 1 law 2;? /9. J2

| 72) I 1 J INVENTOR Hui/mu D0010 Oct. 5, 1965 3,210,645

REGULATOR ARRANGEMENT FOR LOW-VOLTAGE GENERATORS Filed Nov. 14. 19 61 1-1. DQMANN 3 Sheets-Sheet 2 wrzwrop Oct. 5, 1965 H. DOMANN 3,210,645

REGULATOR ARRANGEMENT FOR LOW-VOLTAGE GENERATORS Filed Nov. 14, 1961 3 Sheets-Sheet 3 United States Patent 3,210,645 REGULATOR ARRANGEMENT FOR LOW- VOLTAGE GENERATORS Helmut Domann, Stuttgart, Germany, assignor to Robert Bosch G.m.b.H., Stuttgart, Germany Filed Nov. 14, 1961, Ser. No. 152,240 Claims priority, application Germany, Dec. 11, 1959, B 55,868; Nov. 26, 1960, B 60,247 6 Claims. (Cl. 322--28) The present application is a continuat-ion-in-p-art of my earlier application Serial No. 73,703, filed December 5, 1960, now US. Patent 3,106,673 and entitled Regulating Device for Electric Generators of Low Voltage, especially for Light Generators of Motor Cars.

The present invention concerns a regulator arrangement for low-voltage generators which may be driven at greatly varying speeds. This applies particularly to the lighting generators of motor vehicles.

Regulator arrangements of the type set forth are known which comprise a transistor connected in the exciter circuit of the generator, the collector of the transistor being connected with one end of the exciter winding of the generator, the base of the transistor being connected with the operable contacts of an electromagnetic relay the energizing coil whereof is connected so as to be passed by a current varying in proportion with the varying output voltages of the generator. In such conventional regulator arrangements the contacts of the electromagnetic relay controlled by the output voltage which is to be regulated, are moved to open position whenever the output voltage of the generator is about to exceed a predetermined normal value. Therefore, the relay contacts are located in a line connecting the base of the transistor with that one of the out-put terminals of the generator which is also connected with the collector of the transistor.

It has been found that an arrangement of this particular type easily causes contact troubles because at the moment when the cooperating contacts are separated a very considerable voltage may appear therebetween. Moreover, it is rather difiicult in such an arrangement to provide for a rapid transition between energized and de-energized condition of the relay so as to assure a sufficiently high frequency of the switching operation of the relay.

'It has been found further that in certain cases one or more of the resistors provided in a regulator circuit develop substantial amounts of heat while the regulator is in operation whereby the functional characteristics thereof are affected.

It is therefore a main object of the present invention to provide for a regulator arrangement which avoids the above mentioned difiiculties.

It is another object of the invention to provide for a regulator arrangement of the general type set forth in which the wattage to be handled at the contacts of the voltage-dependent relay is greatly reduced as compared with the corresponding condition in conventional arrangements.

It is still another object of the invention to provide for a regulator arrangement of the type mentioned in which a high switching frequency of the relay is assured irrespective of the actual inductance of the exciter winding of the generator so that a uniform type of regulator may be utilized in connection with generators of different capacities.

It is still another object of this invention to provide for a regulator arrangement of above type which permits also the incorporation of a tell-tale lamp indicating whether a battery connected in the output circuit of the generator is being charged or not, the particular lamp being sup- 3,210,645 Patented Oct. 5, 1965 posed to be extinguished when the output voltage of the generator reaches the actual voltage available at the terminals of the battery so that with such voltage or a higher voltage the generator is capable to charge the battery.

It is still a further object of the invention to provide for a modification of a regulator arrangement of the type set forth in which undesirable heating of a resistor forming part of the regulator circuit is prevented.

With above objects in View, a regulator arrangement for a low-voltage generator operable at varying speeds and having a first and a second output line carrying opposite polarities, comprises, according to the invention, an exciter coil connected at one end with said first output line, transistor means having an emitter electrode connected with said second output line and a collector electrode connected with the other end of said exciter coil, electromagnetic relay means including a relay winding and a normally open relay switch operable by energization of said relay winding and arranged in parallel with the emitter-base circuit of said transistor means, first resistor means connected between the base of said transistor and one end of said relay winding, second resistor means connected between said one end of said relay winding and one of said ends of said exciter coil, the other end of said relay winding being connected with that one of said output lines which is not connected with that end of said exciter coil with which said second resistor is connected, whereby said transistor is normally conductive so as to pass exciter current through its emitter-collector circuit, but is rendered non-conductive so as to interrupt excitation when through increase of generator output voltage said relay means are energized to shunt the emitter-base circuit of said transistor.

The novel features which are considered as characteriistic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accom panying drawing, in which:

FIG. 1 is a circuit diagram of a lighting plant of a motor vehicle, including a regulator arrangement according to the invention;

FIG. 2 is a graph illustrating the regulating procedure;

FIG. 3 is a graph showing the current-voltage characteristic of a non-linear conductor element provided in the circuit of FIG. 1;

'FIG. 4 is a graph illustrating the voltage-current characteristic of a generator controlled by the regulator arrangement according to the invention;

FIG. 5 is a diagrammatic perspective view of the lighting plant of a vehicle including a generator, a regulator and a battery;

FIG. 6 is a circuit diagram of the lighting plant illustrated by FIG. 5, constituting a modification of the invention; and

FIG. 7 is a circuit diagram illustrating diagrammatically a basic circuit arrangement common to the embodiments illustrated by FIGS. 1-6.

Referring now first to FIG. 7, the arrangement comprises a generator G having an exciter coil F. The output terminals of the generator G are connected by two output lines L and L with the corresponding terminals of a storage battery B. Conventional switches and the like which have no bearing on the invention are omitted in this drawing for the sake of clarity and simplicity. In the output line L a rectifier V is connected for preventing return flow of electric energy from the battery B to the generator G. A second rectifier V is connected for well known purposes in parallel with the exciter coil F. Between the generator arrangement and the storage battery a regulator R according to the invention is inserted. The regulator components are shown within the dotted frame R. The regulator arrangement according to the invention comprises a transistor T which has a base B, and emitter electrode E connected to one of the output lines L while the collector electrode C is connected to that end of the exciter coil F which is not connected to the other output line L A switch relay is provided which comprises a relay winding S and a relay switch A which 'is normally in open position as shown and connected in parallel with the emitter-base circuit of the transistor T. A first resistor R is connected between the base B of the transistor T and one end of the relay coil S and the same end of the winding S is connected to a second resistor R The other end of this resistor and the other end of the relay winding S are respectively connected with the movable contact arms of a double-throw double-pole switch W. By means of the illustrated connections the switch W connects in one of its positions the resistor R via contact 1 with the end of the exciter P which is connected to the collector electrode C of the transistor T, and connects simultaneously the other end of the relay winding S via contact 3 with the output line L which is connected to the end of the exciter coil F opposite to the last mentioned end thereof. However, when the switch W is in its second position, the one end of the relay winding S is connected through the resistor R and contact 2 with the output line L while the other end of the relay winding is connected via contact 4 with the other output line L Depending upon the chosen position of the switch W the regulator will operate according to one or another manner. Of course, if only one manner of operation is desired, the switch W may be omitted and in one case the resistor R would be permanently connected with the junction point between one end of the exciter coil F and the collector electrode C of the transistor T, while simultaneously the other end of the relay winding S would be permanently connected with the output line L If, on the other hand, the other manner of operation is desired, then the one end of the relay winding S would be permanently connected via resistor R directly with the output line L while the other end of the relay winding S would be permanently connected directly with the other output line L The different manners of operation of the regulator mentioned above, and the advantages thereof and of the arrangement just described, will become fully apparent from the following description of more elaborate embodiments of the invention.

FIG. 1 illustrates by way of example the lighting plant of a motor vehicle, not shown. The plant comprises a three-phase alternating current generator which has three stator windings 11, 12 and 13 and an exciter winding 15 carried by a rotary armature not shown. Also the means for driving the rotor are not shown. Each of the stator windings 11, 12 and 13 is connected, respectively, with one of three pairs of rectifiers 16 in a well known manner. The rectifier arrangement is connected between ground and a positive output line 18 which leads across a low-resistance resistor 19 to the positive terminal of a battery 20. The actual regulator arrangement according to the invention is shown within the dotted line frame R. A switch 23 is provided in the line 22 connecting the terminal 33a with the positive terminal of the battery 20. By operating the switch 23 not only the regulator arrangement but also all those components or devices of the vehicle which are to be operated electrically and which are symbolized by the block 25, e.g. the ignition system, signaling means, etc., can be supplied with electrical energy.

The actual regulator arrangement R comprises, first of all, a power transistor of the p-n-p type. The emitter electrode thereof is connected by a line 31 with the positive connection 22 mentioned above. The emitter-collector circuit of the transistor 30 is connected in series with the exciter winding 15 of the generator 10, the other end of the winding 15 being connected to ground and thereby to the negative terminal of battery 20. The collector of the transistor 30 is additionally connected with a silicon diode 32 the input electrode whereof is also connected with ground through the terminal 33 of the regulator arrangement R. As will be explained further below, the diode 32 is designed to protect the transistor 30 against excessive voltages which are to be expected to appear when during the regulation procedure described below the transistor is changed briefly from its conductive condition to its non-conductive condition.

According to the invention a pair of normally open cooperating contacts is connected in parallel with the emitter-base circuit of the transistor 30. These contacts form part of an electromagnetic relay which has an energizable coil 35 connected between the terminals 33 and 33a so as to be passed by a current J which depends upon the rectified output voltage of the generator 10 and which is usually proportional thereto. The above-mentioned pair of contacts of the relay consists of a switch arm 36 operated by the armature, not shown, of the coil 35, and of a stationary contact 37. The switch arm 36 is connected with the line 31 while the contact 37 is connected with the base electrode of the transistor 30. The contact 37 and thus also the base electrode of the transistor is connected across a fixed resistor 38 with the movable tap of a potentiometer 40 one end of which is connected to the above mentioned coil 35 of the relay while the other end is also connected to the grounded terminal 33. For reasons stated further below, a second stationary contact 42 is provided for cooperation with the switch arm 36. However, the distance between the relay contacts 42 and 37 as well as the distance between the not shown armature and the iron core of the relay, not shown, are so chosen in relation to the action of a return spring, not shown, controlling the relay armature, that the switch arm 36 may be disengaged from the contact 42 whenever the rectified output voltage of the generator exceeds the battery voltage which amounts to about 12.6 volts when the battery 20 is operating under load; however under the just mentioned condition the switch arm 36 would not yet move sufficiently to engage the stationary contact 37 but would be held in an inbetween position between the two stationary contacts 37 and 42 as long as the generator output voltage remains below a predetermined normal value of about 14 volts which is the desired voltage to be determined by the action of the regulator arrangement.

The second stationary contact 42 is connected by a line 43 via terminal 33 with a tell-tale lamp 45, the other terminal whereof is connected to ground. This lamp 45 is intended to light up when the switch 23 is closed while the output voltage of the generator is still below the battery voltage which depends upon the degree of its being discharged or charged. However, the tell-tale lamp 45 is to be extinguished whenever a load current J flows from the rectifiers 16 via line 18 to the battery 20, said load current constituting the charging current for the battery.

For the purpose of protecting the rectifier arrangement 16 and the stator windings 11, 12 and 13 of the generator against overload a current limiting arrangement is provided which causes a considerable reduction of the output voltage of the generator whenever the load current J flowing through the line 18 and through the resistor 19 exceeds a predetermined maximum value. The current limiting arrangement comprises a second coil portion 47 of the above described relay which second coil portion 47 acts on the armature, not shown, and on the switch arm 36 in the same manner as the abovedescribed voltage controlled main coil 35. -As can be seen, the second coil 47 is arranged in an auxiliary circuit including a germanium semi-conductor 48 arranged in parallel with the resistor 19.

The operation of the above described regulator arrangement will be best understood by starting with the consideration that e.g. upon starting of the engine, the generator 10, having been at a standstill, is first caused to start rotation of its rotor under the action of a driving motor not shown in the drawing. Since for starting the just-mentioned motor the switch 23 has to be moved to closed position, a strong exciter current J can be supplied to the exciter winding 15 of the generator through the lines 22 and 31 and through the emittercollector circuit of the transistor 30 which under the prevailing conditions is in conductive condition. The just-mentioned strong exciter current 1 causes a rapid build-up of a direct current field rotating with the rotating armature of the generator. Consequently voltages are produced in the stator windings 11, 12 and 13 which increase the more rapidly the higher is the rotary speed of the generator.

FIG. 2 illustrates in graph form the increase of the rectified output voltage U of the generator appearing between the positive output line 18 and ground, in relation to time t. As long as the output voltage U remains smaller than the battery voltage U marked in FIG. 2 as amounting to 12.6 volts, the current 1 flowing through the voltage responsive coil 35 of the relay is not yet able to lift the switch arm 36 from its cooperating contact 42 with which it is held normally in engagement by spring means not shown. Therefore, the tell-tale lamp 45 is supplied with electric energy from the battery 20 via line 43, contact 42, switch arm 36, line 22 and closed switch 23. Thus the light of lamp 45 indicates that the generator output is not yet able to charge the battery or, in other words, the battery is discharging. When, however, the generator output voltage U at the time t has risen enough to exceed the battery voltage U then the current J increasing in proportion with, or any way depending upon, the voltage U sufiices to lift the switch arm 36 from the contact 42 so that the lamp 45 is extinguished and thus indicates that the battery is now being charged. However, the transistor 30 still remains in conductive condition because the switch arm 36 is for the moment in an intermediate position in which it contacts neither the contact 42 nor the contact 37. The transistor 30 is rendered non-conductive only when the generator output voltage U reaches, at the moment marked t a predetermined value U for normal operation, e.g. 14 volts. At this voltage the current J sufiices for moving the switch arm 36 into engagement with the stationary contact 37 whereby the emitter-base circuit of the transistor 30 is shunted, or, in other words the potential of the base electrode of the transistor 30 is raised to such an extent that the transistor cannot remain conductive any longer. Thus, as is also shown in FIG. 2, the current I drops steeply to a value close to Zero and the exciter current J drops accordingly. This drop of the exciter current results in a corresponding collapse of the magnetic field produced by the winding 15, and the resulting self-induced current is permitted to flow through the secondary circuit containing ground, terminal 33, rectifier diode 32, terminal 33' and winding 15. Simultaneously with the collapse of the magnetic field of the exciter winding also the output voltage U of the generator drops. Due to the specific arrangement of the contacts of the relay and the parameters of the relay the desired eifect is assured, namely the effect that upon a small drop of the generator output voltage U the switch arm 36 disengages itself from the main operative contact 37 whereby the transistor 3t) is re turned to its original, normal conductive condition. Upon this slight drop of output voltage the transistor current I is started again as can be seen in FIG. 2. Thereby the magnetic field of the exciter winding 15 is rapidly returned to its previous value so that the whole 6 cycle, just described, repeats periodically as indicated by FIG. 2, without, however, the switch arm 36 being able to return into engagement with the second contact 42.

Since during conductivity of the transistor the po tential difference between its emiter and base amounts to only about .3 to .5 volts, evidently the wattage to be handled between the contact members 36, 37 during the switching operations is kept at an extremely low value, particularly also because the resistor 38 connected in circuit with the base electrode of the transistor and with the contact 37 can be chosen so as to have a comparatively large resistance. It can be seen also that in addition the particular arrangement of the second relay contact 42 results in a reliable control of the tell-tale lamp 45 without requiring for the control of this lamp a separate relay as is customary in known arrangements.

A further remarkable advantage of the arrangement described above consists in the fact that the frequency of the regulatory voltage changes effected by the switching movements of the contact members 36 and 37, does not depend upon the speed of the build-up and collapse, respectively, of the magnetic field in the generator. As can be seen, as soon as the switch arm 36 engages the stationary contact 37 a current is able to flow through this pair of contacts which is slightly greater than the base current flowing during conductivity of the transistor through the resistor 38 and through the emitter-base circuit of the transistor. This slight increase of current produces across that portion of the potentiometer 40 which is located between the grounded terminal 33 and the movable tap 39 a voltage drop which causes the current J flowing through the relay coil to decrease slightly. As soon as the magnetic field produced by the coil 35 has followed this decrease of current, the switch arm 36 already disengages itself again from the contact 37. Thus, a vibratory or oscillatory operation of the switch arm 36 is created which results in a very accurate voltage regulation and entails the further advantage that the regulator arrangement can be used for generators of different capacities. Moreover, the adjustability of the movable tap 39 of the potentiometer makes it possible in an easy manner to adjust the frequency of the regulatory voltage changes to the requirements of different generator sizes or types.

The current limiting arrangement mentioned further above and comprising the resistor 19, the second relay coil 47 and the germanium semi-conductor 48 is designed to cancel out the above-described voltage regulation as soon as the line 32 is connected with current consuming devices 25 which have so low a resistance that, if the output voltage U of the generator were left unchanged, a load current J would result which might overload the generator 10. In the arrangement as shown the load current I produces across the resistor 19 a voltage drop U which, as it increases produces the flow of a control current I across the second relay winding or coil 47. The parameter-s of this auxiliary circuit may be chosen for instance so that a suitable control current I is caused to flow when the voltage U exceeds a value of about .25 volt. This will depend greatly upon the characteristic of the semi-conductor 48. The graph of FIG. 3 illus trates a typical characteristic .of a semiconductor rectifier 48 which displays at a potential difference U of .25 volt between the electrodes of the semi-conductor a very distinct break. A germanium semi-conductor of this type contains a high percentage of copper atoms in an alloyed zone produced by addition of indium in a n-germanium disc, and this type of semi-conductor is particularly well suited for the purpose in question because they not only display a very sharp break in their current-voltage characteristic, but are capable of reaching this break already at very low values of the potential difference U existing between their electrodes.

For the purpose of illustration, the graph FIG. 4 shows the voltage-current characteristic of a direct current generator having a capacity of 400 watts cooperating with a 12 volt battery. A curve 50 indicating 400 watt output is shown. The characteristic indicating the regulation of the output voltage U in relation to increasing load currents 1;, shows that the regulator arrangement above described causes the regulated voltage U of the generator to drop steeply as soon as the load current I increases beyond 27 ampere-s. The product of 14 volts with 27 amperes is close to 400 watts. The sharp break in the characteristic shown in FIG. 4 is desirable because in this manner the capacity of the generator can be utilized most effectively and economically.

FIGS. 5 and 6 illustrate a further rather elaborate and improved embodiment of the invention.

As can be seen from FIG. 5, the generator 110 is driven by means of driving arrangement including grooved sheaves 111 and 112 and V-belts 113 from some rotary member of an engine not shown in detail. Assuming that the engine mentioned above is an engine driving a motor vehicle it will be understood that the rotary speed of the generator shaft 117 will vary greatly depending upon trafficconditions and the like. The generator 1110 contains a direct current armature 116 and an exciter field winding 115, not shown in FIG. 5 but appearing in FIG. 6. The output voltages produced in the armature winding,'not shown, are delivered through a negative brush 118 and a positive brush 119, not shown in FIG. 5, to plug sockets tor terminals 136 and 137, respectively.

In order to keep the output voltage of the generator on as constant as possible a value within the entire range of occurring rotary speeds and loads, a regulator 120 is provided which is connected by four cables 121, 122, 123 and 124 terminating in a multiple plug 125 with a multiple plug socket 127 mounted on the housing of the generator 110 having in its interior four sockets 131, 132, 133 and 134 as indicated in FIG. 6.

The load current of the generator is supplied via the above-mentioned insulated terminals 136 and 137 to a storage battery 140, the negative terminal 141 thereof being connected to ground, while the positive terminal 142 is connected via cable 143 with the terminal 136 of the generator. The terminal 137 is connected to ground. It can be seen that the battery connections are not connected in any way with the regulator 120. Referring now to-the details illustrated by FIG. 6, it will be noted that the terminal 136 is connected with the positive brush 119 via a low resistance 144 of about .025 ohm and a rectifier 145 acting as a return-current block. A line 146 is taken from the brush 119 to the socket 131, a line 147 is taken from a junction point between the resistor 144 and the rectifier 145 to the socket 132. One end of the exciter coil 115 is connected with the negative brush 118, while the other end of the coil 115 is connected directly with the socket 133, and is additionally connected via a germanium diode 148 both with the socket 134 and with the terminal 137. The germanium diode 148 opposes a current flow therethrough as long as an exciter current 1., is supplied from the transistor 150 of the regulator 120 to the exciter coil 115. However, the diode 148 permits the passage of a differential current I produced inductively in the coil 115 when the exciter 1 is periodically interruptedby the regulator arrangement 120 described below, for the purpose of keeping the output voltage of the generator at a substantially constant level.

The regulator arrangement 120 comprises, in addition to the already mentioned transistor 150, an electromagnetic relay which has two windings 153 and 155 and a normally open relay contact pair 151, 152 which can be moved to closed position upon energization of the relay. The emitter-collector circuit of the transistor 150 is connected between the lines 122 and 123. The relay switch 151, 152 is connected, as can be seen, in parallel with the emitter-base circuit of the transistor 150. In the c'ircuitasshown, the transistor 150 is normally in conductive condition, but it is rendered non-conductive upon closing of the contacts 151, 152. This is to be done whenever the output voltage of the generator tends to exceed a normal predetermined value of e.g. 14 volts. For this purpose the relay comprises the above mentioned winding 153 acting as a voltage coil, and additionally the winding 155 acting as a current coil. Both coils or windings are understood to be mounted on the same core (not shown). The current coil 155 is connected via a highly alloyed germanium semi-conductor 156 in parallel with the above mentioned resistor 144. The contact 151 is directly connected with the emitter E of the transistor 150 while the other relay contact 152 is connected with the base B of the transistor 150, preferably via a resistor 157 of about 5 ohms shown in dotted lines. Additionally, the relay contact 152 is connected with a resistor 158 of about 50 ohms which is connected as a seriesresistance for the voltage coil 153 which is connected with its other end with the grounded generator terminal 137.

In accordance with the invention, the collector C of the transistor 150 is connected with a junction point between resistor 158 and voltage coil 153, across a second resistor 160 of about 1000 ohms. The function of this second resistor is described in greater detail further below and serves to lead a portion of the current flowing through the emitter-collector circuit of the transistor to the voltage coil 153 as long as the transistor is in condition and furnishes the exciter current J however when the transistor 15%) is rendered non-conductive the resistor 160 causes a supply of the voltage coil 153 with a portion of the counter-voltage appearing across the exciter winding and causing the differential current l The operation of the arrangement is as follows: as soon as the generator after stand-still is driven at a sufliciently high rotary speed, the generator excites itself via the transistor which is now in conductive condition and the output voltage increases rapidly to its predetermined normal value of e.g. 14 volts. When the output voltage of the generator has this value, the base current l flowing across the base resistor 157 and the series-resistance 158 has a value large enough for producing a magnetic field that is capable to move the movable relay contact 151, against the force of a not shown return spring, into engagement with the stationary relay contact 152 which is connected in circuit with the base B of the transistor 150. Hereby the emitter-base circuit of the transistor is short-circuited. In this manner the exciter current J flowing up to this moment through the exciter coil 115 is interrupted and the output voltage of the generator will start to decrease at a rate which depends upon the size of the generator. However, the transistor 150 is again rendered conductive as soon as the magnetic field of the relay is not capable any more to hold the movable relay contact 151 in its circuit-closing position.

In order to make it possible that this last-mentioned condition namely the return of the transistor 150 to nonconductive condition takes place as soon as possible without the necessity of the output voltage of the generator dropping substantially below its predetermined normal Value, the above mentioned second resistor is provided. This second resistor functions as follows: as soon as the transistor 150 is rendered non-conductive and the exciter current J stops flowing through the exciter coil 115, a counter-voltage is induced in the exciter coil and causes the flow of a differential current 1,, through the germanium rectifier 48 which had been non-conductive up to this moment. The current J fades within a time period determined by the inductivity of the exciter coil and its ohmic resistance. During this transient period the terminal or socket 133 connected both with the resistor 160 and with the collector C of the transistor 150 carries a potential which is, on account of the flow of the current I about .3 to .5 volt lower than the potential existing at the negative terminal 137. Consequently, a portion of the current now flowing via the closed relay contacts 151, 152 to the relay winding 153 is branched off across the resistor 160 and applied to the terminal or socket 133 so that the energization of the relay is not only not increased, but rather slightly reduced. This reduction of the energization of the relay causes the switch arm 151 to return already to its normal open position whereby the transistor 150 is again rendered conductive as soon as the output voltage starts to drop on account of the excitation being cut off. In this manner a very rapid and sensitive play of the relay contacts between open and closed positions is obtained which is substantially independent from the actual size of the generator which cooperates with the particular regulator arrangement. The resulting advantage is a greatly increased accuracy and stability of the regulating procedure, and also the possibility of using one particular regulator type with generators of greatly varying capacities or sizes.

For best results it is advisable that the resistance value of the second resistor 160 is at least five times, but not more than 50 times, and preferably 20 to 30 times as large as the series resistance 158 connected with one end of the relay winding and with one end of the second resistor 160. It is further advisable to select for the base resistor 157 a resistance value which causes the switching voltage appearing between the relay switch contacts 151, 152 to be at least .8 volt, preferably 1 volt'.

When the diode portions in the transistor 150 and in the rectifier 148 are made of germanium, then the potential difference across these diodes appearing when they are operated in direction of their conductivity generally does not exceed about .5 volt. If the diodes are made of silicon then this potential difference rarely exceeds .8 volt. If now these potential differences are designated U then the resistance value R of the second resistor 160 in relation to the resistance value R of the series resistor 58 with respect to the predetermined normal value U of the generator output voltage existing between the terminals or sockets 132 and 133 is to be selected in accordance with the following equation:

wherein c is a factor ranging between .90 and .98.

The current winding 155 of the relay serves only the purpose of reducing strongly the voltage output of the generator when the load current furnished via output line 143 to the battery 140 or other users tends to exceed a predetermined maximum value. This constitutes a protection for the generator against overload. The voltage drop across the resistor 144 caused by the load current gives rise to a control current J flowing through the line 146 and the semi-conductor 156, through winding 155 and back through line 147, as soon as this voltage drop across resistor 144 exceeds the critical voltage of about .3 volt of the semi-conductor 156. The control current J creates in the current winding 155 an additional magnetic field which increases the magnetic excitation of the relay Where by the movable contact 151 is held in circuit-closing condition rendering the transistor 150 non-conductive even when the output voltage of the generator is below the predetermined normal value thereof.

It will be understood that each of the elements described above or two or more together, may also find a useful application in other types of regulator arrangements for generators differing from the types described above.

While the invention has been illustrated and described as embodied in regulator arrangement for low-voltage generator operable at varying speeds, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. A regulator arrangement for a low-voltage generator operable at varying speeds and having a first and a second output line carrying opposite polarities, comprising, in combination, an exciter coil having two ends and being connected at one end with said first output line; transistor means having a base electrode, and having an emitter electrode connected with said second output line, and a collector electrode connected With the other end of said exciter coil; electromagnetic relay means including a relay winding and a normally open relay switch operable by energization of said relay winding and arranged in parallel with the emitter-base circuit of said transistor means; first resistor means connected between said base electrode of said transistor means and one end of said relay winding; second resistor means connected between said one end of said relay winding and the other end of said exciter coil, the other end of said relay winding being connected with that one of said output lines which is not connected with said other end of said exciter coil with which said second resistor is connected, whereby said transistor is normally conductive so as to pass exciter current through its emitter-collector circuit, but is renered non-conductive so as to interrupt excitation when through increase of generator output voltage said relay means are energized to shunt the emitter-base circuit of said transistor.

2. A regulator arrangement for a low-voltage generator operable at varying speeds and having a first and a second output line carrying opposite polarities, comprising, in combination, an exciter coil having two ends and being connected at one end with said first output line; transistor means having a base electrode, and having an emitter electrode connected with said second output line, and a collector electrode connected with the other end of said exciter coil; electromagnetic relay means including a relay winding and a normally open relay switch operable by energization of said relay winding and arranged in parallel with the emitter-base circuit of said transistor means; first resistor means connected between said base electrode of said transistor means and one end of said relay winding; second resistor means connected between said one end of said relay winding and the other one of said ends of said exciter coil, the other end of said relay winding being connected with said first output line, whereby said transistor is normally conductive so as to pass exciter current through its emitter-collector circuit, but is rendered non-conductive so as to interrupt excitation when through increase of generator output voltage said relay means are energized to shunt the emitter-base circuit of said transistor.

3. Regulator arrangement for a low-voltage generator operable at varying speeds and having an output circuit and an exciter circuit, said arrangement comprising, in combination, transistor means having an emitter electrode and a collector electrode connected in series with the exciter circuit of the generator, and having a base electrode connected with the generator output circuit so as to normally render said transistor conductive; relay means having coil means and a first control resistor connected in series therewith, the resulting series-combination being connected with the generator output circuit for being energized by a predetermined current depending upon the varying output voltage of the generator and controlled by said first control resistor, and normally open contact means operable by energization of said coil means by said predetermined current and connected in parallel with the emitter-base circuit of said transistor means so as to render said transistor means non-conductive When'said contact means are changed to closed position upon energization of said coil means depending upon a predetermined value of said generator output voltage, a second control resistor being connected between said collector electrode and a junction point within said series-combination for applying, when said transistor means are conductive, a portion of an exciter current passing through the emitter-collector circuit of said transistor means to said relay coil means, and for applying, when said transistor means is rendered non-conductive, a portion of the counter-voltage then developing across said exciter circult to said relay coil means.

4. An arrangement as claimed in claim 3, wherein the resistance of said second control resistor is at least five times and at most fifty times that of said first control resistor.

5. Regulator arrangement for a low-voltage generator operable at varying speeds and having an output circuit and an eXciter circuit, said arrangement comprising, in combination, transistor means having an emitter electrode and a collector electrode connected in series with the exciter circuit of the generator, and having a base electrode connected with the generator output circuit so as to normally render said transistor conductive; currentresponsive resistor means in said output circuit for producing a voltage differential proportional to a load current flow in said output circuit; relay means having first coil means in circuit with said current-responsive resistor means for being eifectively energized by a predetermined current applied thereto when said voltage differential reaches a predetermined value, and independent second coil means and a first control resistor connected in series therewith, the resulting series combination being connected with the generator output circuit for being energized by a predetermined current depending upon the varying output voltage of the generator and controlled by said first control resistor, and normally open contact means operable by energization of at least one of said coil means by at least one of said predetermined currents and connected in parallel with the emitter-base circuit of said transistor means so as to render said transistor means nonconductive when said contact means are changed to closed position upon energization of at least one of said coil means, a second control resistor being connected between said collector electrode and a junction point within said series-combination for applying, when said transistor means are conductive, a portion of an exciter current passing through the emitter-collector circuit of said transistor means to said second relay coil means, and for applying, when said transistor means is rendered non-conductive, a portion of the counter-voltage then developing across said eXciter circuit to said second relay coil means.

6. An arrangement as claimed in claim 5, wherein semiconductor means characterized by a predetermined threshold voltage valueare connected between said ourrent-responsive resistor means and said first coil means for causing eifective energization thereof only when said voltage differential exceeds said threshold voltage value.

References Cited by the Examiner FOREIGN PATENTS 199,756 9/58 Austria.

LLOYD MCCOLLUM, Primary Examiner. 

1. A REGULATOR ARRANGEMENT FOR A LOW-VOLTAGE GENERATOR OPERABLE AT VARYING SPEEDS AND HAVING A FIRST AND A SECOND OUTPUT LINE CARRYING OPPOSITE POLARITIES, COMPRISING, IN COMBINATION, AN EXCITER COIL HAVING TWO ENDS AND BEING CONNECTED AT ONE END WITH SAID FIRST OUTPUT LINE; TRANSISTOR MEANS HAVING A BASE ELECTRODE, AND HAVING AN EMITTER ELECTRODE CONNECTED WITH SAID SECOND OUTPUT LINE, AND A COLLECTOR ELECTRODE CONNECTED WITH THE OT HER END OF SAID EXCITER COIL; ELECTROMAGNETIC RELAY MEANS INCLUDING A RELAY WINDING AND A NORMALLY OPEN RELAY SWITCH OPERABLE BY ENERGIZATION OF SAID RELAY WINDING AND ARRANGED IN PARALLEL WITH THE EMITTER-BASE CIRCUIT OF SIAD TRANSISTOR MEANS; FIRST RESISTOR MEANS CONNECTED BETWEEN SAID BASE ELECTRODE OF SAID TRANSISTOR MEANS AND ONE END OF SAID RELAY WINDING; SECOND RESISTOR MEANS CONNECTED BETWEEN SAID ONE END OF SAID RELAY WINDING AND THE OTHER END OF SAID EXCITER COIL, THE OTHER END OF SAID RELAY WINDING BEING CONNECTED WITH THAT ONE OF SAID OUTPUT LINES WHICH IS NOT CONNECTED WITH SAID OTHER END OF SAID EXCITER COIL WITH WHICH SAID SECOND RESISTOR IS CONNECTED, WHEREBY SAID TRANSISTOR IS NORMALLY CONDUCTIVE SO AS TO PASS EXCITER CURRENT THROUGH ITS EMITTER-COLLECTOR CIRCUIT, BUT IS RENERED NON-CONDUCTIVE SO AS TO INTERRUPT EXCITATION WHEN THROUGH INCREASE OF GENERATOR OUTPUT VOLTAGE SAID RELAY MEANS ARE ENERGIZED TO SHUNT THE EMITTER-BASE CIRCUIT OF SAID TRANSISTOR. 